21β-Hydroxy-oleanane-type triterpenes from Hippocratea excelsa (original) (raw)

Stem bark of Hippocratea excelsa afforded six pentacyclic triterpenes, five oleanane and one ursane types. They were identified as 11b,21b-dihydroxy-olean-12-ene-3-one (2), 3a,11a,21b-trihydroxy-olean-12-ene (3), 3a,21b-dihydroxy-11a-methoxy-olean-12-ene (4), 3a,21b-dihydroxy-olean-9(11),12-diene (5), 3a,21b-dihydroxy-olean-12-ene (6) and 3a,21b-dihydroxy-11a-methoxy-urs-12-ene, isolated as its diacetate derivative , as well as 3a,21b-dihydroxy-olean-12-ene (1) previously isolated from the root bark. The known a-and b-amyrin, oleanoic and ursolic acids, trans-polyisoprene, and the ubiquitous b-sitosterol were also isolated. Structures were elucidated on the basis of spectroscopic analyses, including homo-and heteronuclear correlation NMR experiments (COSY, ROESY, HSQC and HMBC) and comparison with literature data. The antigiardial activity of compounds 2-5 was not significant.